Composition containing retinal

ABSTRACT

A retinal-containing cosmetic skin-care composition comprising an oil-in-water emulsion stabilized by BHT and a method for preparing same.

This is a 371 of PCT/FK95100250 filed Mar. 22, 1995.

The present invention relates to new dosage forms suitable for topical application and containing retinal.

Health-care products containing retinoids have become a focus of interest in recent years. Retinoic acid, also known by the name of vitamin A acid or tretinoin, is used in the treatment of acne, and compositions containing vitamin A acid are numerous and varied.

More recently, other applications of retinoids have been put forward, for instance light-induced aging. In effect, individuals who are exposed to large amounts of sunlight during their childhood display the following skin features in adulthood: wrinkled, furrowed, yellow, slack, rough, dry and blemished (hyperpigmentation) skin and various premalignant growths. These phenomena are more marked in fair-skinned individuals, who often burn in the sun and do not tan very much.

Before these skin manifestations appear clinically, serious adverse changes in the epidermis and dermis may be observed microscopically in young subjects who have received a large amount of exposure.

U.S. Pat. No. 4,603,146 describes the treatment of skin damaged by exposure to sunlight, using a preparation containing vitamin A acid in an emollient excipient. Later, in U.S. Pat. No. 4,877,805, it is taught that retinoids may be used to prevent and repair the damage caused by sunlight on human skin.

It is also known that the use of retinal (vitamin A aldehyde) is preferred to that of retinoic acid on account of its better skin tolerability. In effect, retinal (vitamin A aldehyde) occurs naturally in human metabolism: it is used, in particular, in treatments designed to improve vision.

However, retinal is a compound displaying poor physicochemical stability; its formulation in a form displaying good organoleptic qualities as well as good storage characteristics has not been achieved satisfactorily to date.

In the context of the present invention, the active retinal may be in 13-cis or 13-trans form or the form of all other mixtures of these isomers.

On storage, other forms tend to appear, such as 9-cis-retinal, 11-cis-retinal or condensation products of the polymer type, which are inactive.

U.S. Pat. No. 4,826,828 has proposed the use of volatile silicones and ethanol for the preparation of compositions containing retinol; these preparations may be diluted before application by formation of a water-in-oil emulsion.

U.S. Pat. No. 4,720,353 describes water-in-oil emulsions stabilized by a particular organopolysiloxane.

However, these formulations do not give satisfactory results on storage.

Application WO 93/00085 describes formulations of retinoids in the form of a water-in-oil emulsion, stabilized by a complex system comprising a chelating agent and water-soluble and fat-soluble antioxidant.

These formulations entail a large number of parameters which are difficult to implement. In addition, water-in-oil emulsions are poorly suited to topical application, especially in cosmetology.

Accordingly, the subject of the present invention is a dermocosmetological composition containing retinal, characterized in that it consists of an oil-in-water emulsion stabilized essentially by one or more fat-soluble antioxidants.

Oil-in-water emulsions according to the present invention possess good spreading capacities without a greasy feel. The specific stabilization system enables the phenomena of degradation over time which are observed with the conventional oil-in-water emulsions to be limited.

Antioxidants which are especially suitable for obtaining a stabilization system according to the invention may be chosen from the group comprising: butylated hydroxytoluene (BHT), butylated hydroxyanisole (BHA), ascorbyl palmitate, alpha-tocopherol and its esters, citric acid, propyl gallate and/or mixtures thereof.

The alpha-tocopherol may be, in particular, in acetate form.

The retinal present in the composition is incorporated in the oily (internal) phase of the emulsion. The retinal will thus be better protected from aerial oxygen than if it were in the external phase (in a water-in-oil emulsion, for example) and hence in direct contact with the air.

In general, the retinal concentration in the composition according to the invention is at least 0.01% by weight, and can reach as much as approximately 1% by weight of the total composition.

Preferred concentrations for the retinal are between 0.04 and 0.06% by weight, and will be more especially approximately 0.05%.

Preferably, the concentration of fat-soluble antioxidants in the oily phase is between 0.005% and 0.5% by weight.

These concentrations will vary in accordance with the antioxidant used. For example, BHT or BHA will each be present at approximately 0.01% to 0.03% by weight. The concentrations of alpha-tocopherol or its esters can reach 0.5%, and are preferably greater than 0.05%, by weight.

An important factor for the stability of the emulsions is the ratio of the concentrations of fat-soluble antioxidants to the retinal concentrations. Especially advantageous results in terms of stability on storage are obtained when the fat-soluble antioxidant/-retinal concentration ratio is between 0.1 and 0.6, in particular when the ratio is approximately 0.4.

The oily phase can contain mineral and/or organic oils, polar or otherwise, waxes, esters and silicones. Depending on the desired physical characteristics, the compositions according to the invention can also contain surfactants, gelling thickeners, perfumes and colorants.

The pH of the compositions is preferably slightly acid or close to neutrality for the purpose of its sic! application to the skin; compositions according to the invention have, in particular, a pH of between 6 and 7.5.

According to one of its aspects, the subject of the invention is an oil-in-water emulsion, characterized in that it contains retinal at a concentration of between 0.04% and 0.06% by weight, preferably of approximately 0.05%, and BHT at a concentration of between 0.01% and 0.03%, preferably of approximately 0.02%, by weight.

According to yet another aspect, the invention relates to an oil-in-water composition, characterized in that it contains retinal at a concentration of between 0.04% and 0.06% by weight, preferably of approximately 0.05%, and propyl gallate at a concentration of between 0.01% and 0.03%, preferably of approximately 0.02%, by weight.

The invention comprises the cosmetic use of the oil-in-water emulsions thus defined.

It also comprises the use as medicament of the retinal-based compositions displaying one or more of the above features.

Lastly, the present invention also extends to a process for preparing the oil-in-water compositions, which entails the following steps:

a) retinal is dissolved in one or more organic and/or mineral oils,

b) one or more fat-soluble antioxidants is/are added to the solution,

c) the solution obtained is emulsified in an aqueous and/or aqueous-alcoholic solution to obtain an oil-in-water emulsion.

The examples which follow are designed to illustrate the invention without in any way limiting its scope.

EXAMPLE 1 Qualitative study of stabilization of retinal

In a first stage, different lipophilic antioxidants were tested in order to define the one which stabilizes retinal best:

The antioxidants tested are:

    ______________________________________                                          BHA                                                                             Butylated hydroxyanisole                                        BHT                                                                             Butylated hydroxytoluene                                        PROPYL GALLATE                                                   RONOXAN.sup.(R) A                                                               Alpha-tocopherol  5%                                                           Ascorbyl palmitate                                                                              25%                                                           Q. S. lecithin                                                 0 RONOXAN.sup.(R) 582                                                            Ascorbyl palmitate                                                                              15%                                                           Mono- and diglyceride                                                                           85%                                            RONOXAN.sup.(R) 583                                                             Ascorbyl palmitate                                                                              11%                                                           Alpha-tocopherol 11%                                                           Citric acid       3%                                                           Mono- and diglyceride                                                                           75%                                            ALPHA-TOCOPHEROL                                                 ACETATE                                                          TOCOPHEROL                                                      ______________________________________                                    

Retinal (vitamin A aldehyde) is solubilized at a concentration of 0.05% in 2 oils: one polar, namely Miglyol® 812 (caprylic triglycerides), the other nonpolar, namely Cosbiol® (squalane).

Results

                  TABLE 1                                                          ______________________________________                                         0.05% solution of retinal (vitamin A aldehyde) in a polar                      oil (Miglyol.sup.(R) 812: capric/caprylic triglycerides).                                   Storage at room                                                                            Amount of trans-retinal                               Antioxidant  temp. ≅ 20° C.                                                            remaining (%)                                         ______________________________________                                         BHA, 0.01%   T 1 month   92.8%                                                              T 6 months  76%                                                   BHT, 0.01%   T 1 month   92.4%                                                              T 6 months  78.4%                                                 PROPYL GALLATE                                                                              T 1 month   91.4%                                                 0.01%        T 6 months  73.7%                                                 RONOXAN.sup.(R) A                                                                           T 1 month   90%                                                   0.1%         T 6 months  60.2%                                                 RONOXAN.sup.(R) 582                                                                         T 1 month   94.1%                                                 0.1%         T 6 months  78.4%                                                 RONOXAN.sup.(R) 583                                                                         T 1 month   88.2%                                                 0.1%         T 6 months  75.2%                                                 ALPHA-TOCOPHEROL                                                                            T 1 month   90.7%                                                 ACETATE +    T 6 months  73.8%                                                 TOCOPHEROL 0.2%                                                                Control without                                                                             T 1 month   81.3%                                                 antioxidant  T 6 months  41.4%                                                 ______________________________________                                    

                  TABLE 2                                                          ______________________________________                                         0.05% solution of retinal (vitamin A aldehyde) in a                            nonpolar oil (Cosbiol: squalane).                                                           Storage at room                                                                            Amount of trans-retinal                               Antioxidant  temp. ≅ 20° C.                                                            remaining (%)                                         ______________________________________                                         BHA, 0.01%   T 1 month   99.4%                                                              T 6 months  75%                                                   BHT, 0.01%   T 1 month   94.8%                                                              T 6 months  73.5%                                                 PROPYL GALLATE                                                                              T 1 month   97.3%                                                 0.01%        T 6 months  76.4%                                                 RONOXAN.sup.(R) A                                                                           T 1 month    90.55%                                               0.1%         T 6 months  69.6%                                                 RONOXAN.sup.(R) 582                                                                         T 1 month    91.44%                                               0.1%         T 6 months  69.7%                                                 RONOXAN.sup.(R) 583                                                                         T 1 month   98.2%                                                              T 6 months  78.5%                                                 ALPHA-TOCOPHEROL                                                                            T 1 month   91.9%                                                 ACETATE +    T 6 months  76.2%                                                 TOCOPHEROL 0.2%                                                                Control without                                                                             T 1 month   85.6%                                                 antioxidant  T 6 months  43.7%                                                 ______________________________________                                    

Conclusion

The qualitative study of the lipophilic antioxidants in relation to the stabilization of retinal (vitamin A aldehyde) reveals good results with RONOXAN 582, RONOXAN 583, PROPYL GALLATE, BHA and BHT, in both of the solvents Miglyol 812® (R) and Cosbiol.

EXAMPLE 2 Qualitative study of protection of a mixture of fats

A systematic study of protection against oxidation of a mixture of fats and its emulsifying system was carried out with the same antioxidants as those described in the preceding section.

The fatty phase adopted corresponds to an optimal cosmetic mixture, which will be introduced subsequently into an aqueous phase to produce an oil-in-water emulsion.

The composition of this phase is as follows:

    ______________________________________                                          Neobee 18.sup.(R) hybrid safflower oil                                                    10     g                                              Heavy liguid petrolatum                                                                   5      g                                              Cremophor RH 40.sup.(R)                                          (hydrogenated and ethoxylated castor oil)                                                 1      g                                              Simulsol 165.sup.(R)                                             (PEO glycerol monostearate)                                                               8.5    g                                              Wax E (microcrystalline)                                                                  1.5    g                                              Acetulan.sup.(R) (acetylated lanolin alcohols)                                            2      g                                              Neobee M5.sup.(R) (coconut triglycerides)                                                 9      g                                              Solulan PB 10.sup.(R)                                            (propoxylated lanolin ether)                                                              1.5    g                                              2-Phenoxyethanol                                                                          0.5    g                                              Methyl para-hydroxybenzoate                                                               0.2    g                                              Butyl para-hydroxybenzoate                                                                0.1    g                                             Total                     39.3   g                                             ______________________________________                                    

NB The aqueous phase which will be added subsequently will constitute 60.7% of the formula, making 100% in total.

Results

The peroxide value was assayed at time 0 and after 6 months of storage at room temperature in the region of 20° C.

    ______________________________________                                         Mixture of fats and the      Peroxide value                                    emulsifying system in g                                                                      Antioxidant    T0     T6 months                                  ______________________________________                                         Neobee 18  10     BHA 0.01 g     7.93 10.13                                    Heavy liquid                                                                              5      BHT 0.01 g     7.78 7.65                                     petrolatum                                                                     Cremophor RH 40                                                                           1      PROPYL GALLATE 7.73 8.84                                                       0.01.g                                                       Simulsol 165                                                                              8.5                                                                 Wax E      1.5    RONOXAN A.sup.(R)                                                                             8    6.33                                     Acetulan   2      0.1 g                                                        Neobee M5  9      RONOXAN 582.sup.(R)                                                                           7.48 6.59                                     Solulan PB 10                                                                             1.5    0.1 g                                                        2-Phenoxyethanol                                                                          0.5    RONOXAN 583.sup.(R)                                                                           6.67 9.83                                     Methyl     0.2    0.1 g                                                        para-hydroxy-                                                                  benzoate                                                                       Butyl             ALPHA-TOCOPHEROL                                                                              8.57 9.48                                     para-hydroxy-                                                                             0.1    ACETATE O.1 g                                                benzoate          ALPHA TOCOPHEROL                                                                              7.26 20.66                                                      0.1 g                                                                          Control without                                                                               9    30.52                                                      antioxidant                                                  ______________________________________                                    

Conclusion

This study of protection against oxidation of a mixture of fats reveals good results with RONOXAN® 582, RONOXAN® 583, propyl gallate, BHA and alphatocopherol acetate, and BHT in particular.

EXAMPLE 3 Quantitative study with BHT

A quantitative study of stabilization of retinal in an oil-in-water emulsion was conducted with BHT (butylated hydroxytoluene), which had given very good results in the preceding study.

The emulsion adopted was stored for 6 months at room temperature (in the region of 20° C.).

The retinal was assayed in the emulsion at different storage times.

Form of the oil-in-water emulsion

    ______________________________________                                         (Formula 1      Retinal     0.05%                                              (Formula 2      Retinal     0.025%                                             ______________________________________                                    

Fatty phase

    ______________________________________                                         BHT                0.01%                                                       Neobee 18          10%                                                         Heavy liqiiid petrolatum                                                                          5%                                                          Cremophor RH 40    1%                                                          Simulsol 165       8.50%                                                       Wax E              1.50%                                                       Acetulan           2%                                                          Neobee M5          10%                                                         Solulan PB 10      1.50%                                                       2-Phenoxyethanol   0.50%                                                       Methyl para-hydroxybenzoate                                                                       0.20%                                                       Triethanolamine    0.30%                                                       ______________________________________                                    

Aqueous phase

    ______________________________________                                         Propylene glycol                                                                              3%                                                              Carbopol 934     0.25%                                                         Purified water qs                                                                            100%                                                                           pH: in the region of 7                                           ______________________________________                                    

    ______________________________________                                                      % of trans-retinal remaining                                                   Formula 1                                                                             Formula 2                                                  ______________________________________                                         T 1 month        98.9%  98.8%                                                  T 2 months     98%      96.9%                                                  T 3 months     96%      94.9%                                                  T 6 months     83%      92.9%                                                  ______________________________________                                    

Conclusion

The excellent results recorded at 6 months, in particular with the formula 2, reveal a good protection of the retinal with BHT in the ratio

    0.01/0.025

    BHT/retinoid

The order of magnitude of this ratio is preserved in the finished product.

Retinal was determined by high performance liquid chromatography under the following conditions:

Apparatus equipped with a normal silica column (5 μ), length 25 cm, internal diameter 0.4 cm, with a variable wavelength detector set at 365 nm.

The eluent phase is composed of 99% hexane, dioxane and isopropanol in the proportions 990:10:1. Its flow rate is 1.5 ml/min.

The sample to be analyzed is dissolved in dioxane, then in isopropanol and in hexane in the proportions of the eluent phase and at a concentration of 1 μg/ml. 20 μl of solution to be analyzed are injected into the chromatograph in isocratic mode and at room temperature; the retinal emerges with a retention time in the region of approximately 7.5 min.

The HPLC results are reproducible with a coefficient of variation of 2.4%.

EXAMPLE 4 Study of the stabilization of retinal in an oil-in-water emulsion

Detailed formula

Aqueous phase

    ______________________________________                                         Purified water gs                                                                              100%                                                           Carbopol 934       0.25%                                                       Propylene glycol                                                                                3%                                                            ______________________________________                                    

Fatty phase

    ______________________________________                                         Neobee 18        10%                                                           Heavy liquid petrolatum                                                                         5%                                                            Cremophor RH 40  1%                                                            Simulsol 165     8.50%                                                         Wax E flakes     1.50%                                                         Acetulan         2%                                                            Neobee M5        10%                                                           Solulan PB 10    1.50%                                                         BHT              0.02%                                                         2-Phenoxyethanol 0.50%                                                         Methyl para-hydroxybenzoate                                                                     0.20%                                                         Triethanolamine  0.30%                                                                          pH: in the region of 7                                        ______________________________________                                    

Results

The emulsion was stored for 18 months at room temperature (in the region of 20° C.), and for 6 months at 40° C. in accelerated aging.

    ______________________________________                                         Storage        % of trans-retinal remaining                                    ______________________________________                                          4 months at room temp.                                                                       100%                                                             4 months at 40° C.                                                                    86%                                                              6 months at room temp.                                                                         95.5%                                                          6 months at 40° C.                                                                    79%                                                             12 months at room temp.                                                                       80%                                                             18 months at room temp.                                                                       76%                                                             ______________________________________                                    

Conclusion

The proposed emulsion displays excellent stability of the retinal, with 95.5% of trans-retinal after 6 months at 40° C. and 76% after 18 months at room temperature.

EXAMPLE 5 Formulation examples

Formula A

    ______________________________________                                         1.  Retinal (trans form)                                                                                0.05%                                                 2.  Hybrid safflower oil (Neobee 18)                                                                   10%                                                    3.  Heavy liquid petrolatum                                                                            5%                                                     4.  Coconut triglycerides (Neobee M5)                                                                  10%                                                    5.  Ethoxylated hydrogenated castor oil                                                                1%                                                         (Cremophor RH 40)                                                          6.  Glycerol monostearate/PEO                                                                          8.5%                                                       (Simulsol 165)                                                             7.  Microcrystalline wax (Wax E)                                                                       1.5%                                                   8.  Acetylated lanoline alcohols                                                                       2%                                                         (Acetulan)                                                                 9.  Propoxylated lanoline ether                                                                        1.5%                                                       (Solulan PB 10)                                                            10. Butylated hydroxytoluene                                                                            0.02%                                                 11. 2-Phenoxyethanol    0.5%                                                   12. Propyl para-hydroxybenzoate                                                                        0.4%                                                   13. Butyl para-hydroxybenzoate                                                                         0.2%                                                   14. Carbopol 934         0.25%                                                 15. Propylene glycol    3%                                                     16. Triethanolamine qs                                                                           pH ≅ 6.5                                                                       0.3%                                               17. Purified water qs   100                                                                            pH: in the region of 6.5                               ______________________________________                                    

Formula B

    ______________________________________                                         1.  Retinal (trans form)                                                                                0.05%                                                 2.  Hybrid saf flower oil (Neobee 18)                                                                  10%                                                    3.  Heavy liquid petrolatum                                                                            5%                                                     4.  Coconut triglycerides (Neobee M5)                                                                  10%                                                    5.  Ethoxylated hydrogenated castor oil                                                                1%                                                         (Cremophor RH 40)                                                          6.  Glycerol monostearate/PEO                                                                          8.5%                                                       (Simulsol 165)                                                             7.  Microcrystalline wax (Wax E)                                                                       1.5%                                                   8.  Acetylated lanoline alcohols                                                                       2%                                                         (Acetulan)                                                                 9.  Propoxylated lanoline ether                                                                        1.5%                                                       (Solulan PB 10)                                                            10. Butylated hydroxyanisole                                                                            0.02%                                                 11. 2-Phenoxyethanol    0.5%                                                   12. Propyl para-hydroxybenzoate                                                                        0.4%                                                   13. Butyl para-hydroxybenzoate                                                                         0.2%                                                   14. Carbopol 934         0.25%                                                 15. Propylene glycol    3%                                                     16. Triethanolamine qs                                                                           pH ≅ 6.5                                                                       0.3%                                               17. Purified water qs   100%                                                                           pH: in the region of 6.5                               ______________________________________                                    

Formula C

    ______________________________________                                         1.  Retinal (trans form)                                                                                0.05%                                                 2.  Hybrid safflower oil (Neobee 18)                                                                   10%                                                    3.  Heavy liquid petrolatum                                                                            5%                                                     4.  Coconut triglycerides (Neobee M5)                                                                  10%                                                    5.  Ethoxylated hydrogenated castor oil                                                                1%                                                         (Cremophor RH 40)                                                          6.  Glycerol monostearate/PEO                                                                          8.5%                                                       (Simulsol 165)                                                             7.  Microcrystalline wax (Wax E)                                                                       1.5%                                                   8.  Acetylated lanoline alcohols                                                                       2%                                                         (Acetulan)                                                                 9.  Propoxylated lanoline ether                                                                        1.5%                                                       (Solulan PB 10)                                                            10. Ronoxan 582 (ascorbyl palmitate)                                                                   0.2%                                                   11. 2 phenoxyethanol    0.5%                                                   12. Propyl para-hydroxybenzoate                                                                        0.4%                                                   13. Butyl para-hydroxybenzoate                                                                         0.2%                                                   14. Carbopol 934         0.25%                                                 15. Propylene glycol    3%                                                     16. Triethanolamine qs                                                                           pH ≅ 6.5                                                                       0.3%                                               17. Purified water qs   100                                                                            pH: in the region of 6.5                               ______________________________________                                    

Formula D

    ______________________________________                                         1.  Retinal (trans form)                                                                                0.05%                                                 2.  Hybrid safflower oil (Neobee 18)                                                                   10%                                                    3.  Heavy liquid petrolatum                                                                            5%                                                     4.  Coconut triglycerides (Neobee M5)                                                                  10%                                                    5.  Ethoxylated hydrogenated castor oil                                                                1%                                                         (Cremophor RH 40)                                                          6.  Glycerol monostearate/PEO                                                                          8.5%                                                       (Simulsol 165)                                                             7.  Microcrystalline wax (Wax E)                                                                       1.5%                                                   8.  Acetylated lanoline alcohols                                                                       2%                                                         (Acetulan)                                                                 9.  Propoxylated lanoline ether                                                                        1.5%                                                       (Solulan PB 10)                                                            10. Propyl gallate       0.02%                                                 11. 2-Phenoxyethano1    0.5%                                                   12. propyl para-hydroxybenzoate                                                                        0.4%                                                   13. Butyl para-hydroxybenzoate                                                                         0.2%                                                   14. Carbopol 934         0.25%                                                 15. Propylene glycol    3%                                                     16. Triethanolamine qs                                                                           pH ≅ 6.5                                                                       0.3%                                               17. Purified water qs   100%                                                                           pH: in the region of 6.5                               ______________________________________                                     

We claim:
 1. Dermocosmetological composition comprising retinal, in 13-cis or 13-trans form or in the form of a mixture of these isomers, consisting of an oil-in-water emulsion stabilized by a fat-soluble antioxidant consisting of butylated hydroxy toluene (BHT),wherein the concentration of retinal is between 0.01 and 1% by weight, wherein the concentration of BHT is between 0.01 and 0.03% by weight, and wherein the BHT/retinal concentration ratio is between 0.1 and 0.6.
 2. Composition according to claim 1, wherein the retinal is present in the oily phase.
 3. Composition according to claim 1, wherein the fat-soluble antioxidant/retinal concentration ratio is approximately 0.4.
 4. Composition according to claim 1 wherein the pH of the composition is between 6 and 7.5.
 5. Process for preparing a composition according to claim 1 comprising the following steps:a) retinal is dissolved in a solvent selected from the group consisting of an organic oil, a mineral oil, a wax, an ester and a silicone or a mixture of two or more thereof, b) the fat-soluble antioxidant (BHT) is added to the solution, and c) the solution obtained is emulsified in an aqueous or aqueous-alcoholic solution to obtain an oil-in-water emulsionthe concentration of retinal being between 0.01 and 1% by weight, the concentration of BHT being between 0.01 and 0.03% by weight, and the BHT/retinal concentration ratio being between 0.1 and 0.6.
 6. Composition according to claim 1, comprising retinal at a concentration of approximately 0.05% by weight and BHT at a concentration of approximately 0.02% by weight. 